Re: backup to DVD-RAM

Jerry Peters wrote:
> Gary Dale <garydale@rogers.com> wrote:
>> Gary Dale wrote:
>>> Jerry Peters wrote:
>>>
>>>> I've never had any problems, other than DVD-RAM tends to be slow and a
>>>> large amount of buffered writes tend to build up (fixed by mounting
>>>> with the sync option).
>>>>
>>>> What's the "trouble" with working with UDF? My DVD-RAM mounts on
>>>> /dev/sr0 in rw mode and I copy data to it, just as if it were a large
>>>> floppy. That's the advantage of DVD-RAM over the other DVD whatevers,
>>>> it behaves like a large floppy, no special formatting required.
>>>>
>>>> If you really must use growisofs, get the source and change it to your
>>>> needs then.
>>>>
>>> I actually just tried using UDF directly and I found what the problem
>>> is. :)
>>>
>>> It appears that there is a bug in UDF support that isn't fixed until
>>> 2.6.22 (this is from the Wikipedia -
>>> http://en.wikipedia.org/wiki/Universal_Disk_Format) that limits you to
>>> file sizes of no more than 1G. I tarred and zipped the files before
>>> backing them up to save space (even then the tarball is almost 3G), so
>>> my backups failed.
>>>
>>> Still, the growisofs problem of wanting a clean disk bugged me, so I've
>>> switched over to ext2 for now. I test for a file system by trying to
>>> mount it as ext2. If it fails, I format it then mount it.
>>>
>>> Of course, this is not the file system anyone expects on a DVD-RAM disk,
>>> so I will give UDF a try again when Debian/lenny becomes the new stable
>>> release in a couple of years.
>> I'm back to about the only method that seems to be reliable.
>> - mkudffs /dev/dvd -- to blank the DVD-RAM so growisofs will use it
>> - growisofs -Z /dev/dvd /backups
>>
>> For some unknown reason, mke2fs /dev/dvd fails, or if it succeeds, it is
>> unreliable for writing. I may or may not get a complete cp /backups/*
>> /media/dvd but even if I do, I may not be able to mount it again. And
>> even if I can mount it again, there is no guarantee that subsequent cp's
>> will work.
>>
>> In short, working with DVD-RAM seems to be an exercise in frustration
>> even though it is the only game in town for doing repetitive backups.
>> It's supposed ability to be usable just like a hard disk is a myth, at
>> least until kernel 2.16.22.
>
> Never tried ext2. I do use some vfat formatted disks because Win98
> will not consistently recognize UDF DVD-RAM disks (it does recognize
> DVD-ROM's however). Never had any problems except that vfat on DVD is
> slow, of course vfat is slow on a large HD too.
> Could you be having some incompatablity problems with the DVD drive
> itself? Ext2 should work, and modern drives are supposed to handle bad
> sectors internally.
>
> Jerry

I thought perhaps the issue was one of having to do an eject between
operations but my testing gave me similar results with or without an
eject. The main difference is that sometimes it takes two mounts after
an eject - I guess mount times out a bit too fast. This makes testing
for a successful mount a little trickier.

I'm going to stick with growisofs for now, unless it starts giving me
headaches. If it does, I'll try vfat.

Thanks.

Gary Dale <garydale@rogers.com> wrote:
> Jerry Peters wrote:
>> Gary Dale <garydale@rogers.com> wrote:
>>> Gary Dale wrote:
>>>> Jerry Peters wrote:
>>>>
>>>>> I've never had any problems, other than DVD-RAM tends to be slow and a
>>>>> large amount of buffered writes tend to build up (fixed by mounting
>>>>> with the sync option).
>>>>>
>>>>> What's the "trouble" with working with UDF? My DVD-RAM mounts on
>>>>> /dev/sr0 in rw mode and I copy data to it, just as if it were a large
>>>>> floppy. That's the advantage of DVD-RAM over the other DVD whatevers,
>>>>> it behaves like a large floppy, no special formatting required.
>>>>>
>>>>> If you really must use growisofs, get the source and change it to your
>>>>> needs then.
>>>>>
>>>> I actually just tried using UDF directly and I found what the problem
>>>> is. :)
>>>>
>>>> It appears that there is a bug in UDF support that isn't fixed until
>>>> 2.6.22 (this is from the Wikipedia -
>>>> http://en.wikipedia.org/wiki/Universal_Disk_Format) that limits you to
>>>> file sizes of no more than 1G. I tarred and zipped the files before
>>>> backing them up to save space (even then the tarball is almost 3G), so
>>>> my backups failed.
>>>>
>>>> Still, the growisofs problem of wanting a clean disk bugged me, so I've
>>>> switched over to ext2 for now. I test for a file system by trying to
>>>> mount it as ext2. If it fails, I format it then mount it.
>>>>
>>>> Of course, this is not the file system anyone expects on a DVD-RAM disk,
>>>> so I will give UDF a try again when Debian/lenny becomes the new stable
>>>> release in a couple of years.
>>> I'm back to about the only method that seems to be reliable.
>>> - mkudffs /dev/dvd -- to blank the DVD-RAM so growisofs will use it
>>> - growisofs -Z /dev/dvd /backups
>>>
>>> For some unknown reason, mke2fs /dev/dvd fails, or if it succeeds, it is
>>> unreliable for writing. I may or may not get a complete cp /backups/*
>>> /media/dvd but even if I do, I may not be able to mount it again. And
>>> even if I can mount it again, there is no guarantee that subsequent cp's
>>> will work.
>>>
>>> In short, working with DVD-RAM seems to be an exercise in frustration
>>> even though it is the only game in town for doing repetitive backups.
>>> It's supposed ability to be usable just like a hard disk is a myth, at
>>> least until kernel 2.16.22.
>>
>> Never tried ext2. I do use some vfat formatted disks because Win98
>> will not consistently recognize UDF DVD-RAM disks (it does recognize
>> DVD-ROM's however). Never had any problems except that vfat on DVD is
>> slow, of course vfat is slow on a large HD too.
>> Could you be having some incompatablity problems with the DVD drive
>> itself? Ext2 should work, and modern drives are supposed to handle bad
>> sectors internally.
>>
>> Jerry
>
> I thought perhaps the issue was one of having to do an eject between
> operations but my testing gave me similar results with or without an
> eject. The main difference is that sometimes it takes two mounts after
> an eject - I guess mount times out a bit too fast. This makes testing
> for a successful mount a little trickier.
>
> I'm going to stick with growisofs for now, unless it starts giving me
> headaches. If it does, I'll try vfat.
>
> Thanks.

I have 2 different DVD drives, one's a Matsushita and the other is an
LG. I have a number of DVD-RAMS that the Matsushita has trouble
recognizing (the light blinks seemingly forever) while the LG drive
recognizes them without any long delays. I had considered these disks
as defective until trying them in the LG.

Jerry

Jerry Peters wrote:
> Gary Dale <garydale@rogers.com> wrote:
>> Jerry Peters wrote:
>>> Gary Dale <garydale@rogers.com> wrote:
>>>> Gary Dale wrote:
>>>>> Jerry Peters wrote:
>>>>>
>>>>>> I've never had any problems, other than DVD-RAM tends to be slow and a
>>>>>> large amount of buffered writes tend to build up (fixed by mounting
>>>>>> with the sync option).
>>>>>>
>>>>>> What's the "trouble" with working with UDF? My DVD-RAM mounts on
>>>>>> /dev/sr0 in rw mode and I copy data to it, just as if it were a large
>>>>>> floppy. That's the advantage of DVD-RAM over the other DVD whatevers,
>>>>>> it behaves like a large floppy, no special formatting required.
>>>>>>
>>>>>> If you really must use growisofs, get the source and change it to your
>>>>>> needs then.
>>>>>>
>>>>> I actually just tried using UDF directly and I found what the problem
>>>>> is. :)
>>>>>
>>>>> It appears that there is a bug in UDF support that isn't fixed until
>>>>> 2.6.22 (this is from the Wikipedia -
>>>>> http://en.wikipedia.org/wiki/Universal_Disk_Format) that limits you to
>>>>> file sizes of no more than 1G. I tarred and zipped the files before
>>>>> backing them up to save space (even then the tarball is almost 3G), so
>>>>> my backups failed.
>>>>>
>>>>> Still, the growisofs problem of wanting a clean disk bugged me, so I've
>>>>> switched over to ext2 for now. I test for a file system by trying to
>>>>> mount it as ext2. If it fails, I format it then mount it.
>>>>>
>>>>> Of course, this is not the file system anyone expects on a DVD-RAM disk,
>>>>> so I will give UDF a try again when Debian/lenny becomes the new stable
>>>>> release in a couple of years.
>>>> I'm back to about the only method that seems to be reliable.
>>>> - mkudffs /dev/dvd -- to blank the DVD-RAM so growisofs will use it
>>>> - growisofs -Z /dev/dvd /backups
>>>>
>>>> For some unknown reason, mke2fs /dev/dvd fails, or if it succeeds, it is
>>>> unreliable for writing. I may or may not get a complete cp /backups/*
>>>> /media/dvd but even if I do, I may not be able to mount it again. And
>>>> even if I can mount it again, there is no guarantee that subsequent cp's
>>>> will work.
>>>>
>>>> In short, working with DVD-RAM seems to be an exercise in frustration
>>>> even though it is the only game in town for doing repetitive backups.
>>>> It's supposed ability to be usable just like a hard disk is a myth, at
>>>> least until kernel 2.16.22.
>>> Never tried ext2. I do use some vfat formatted disks because Win98
>>> will not consistently recognize UDF DVD-RAM disks (it does recognize
>>> DVD-ROM's however). Never had any problems except that vfat on DVD is
>>> slow, of course vfat is slow on a large HD too.
>>> Could you be having some incompatablity problems with the DVD drive
>>> itself? Ext2 should work, and modern drives are supposed to handle bad
>>> sectors internally.
>>>
>>> Jerry
>> I thought perhaps the issue was one of having to do an eject between
>> operations but my testing gave me similar results with or without an
>> eject. The main difference is that sometimes it takes two mounts after
>> an eject - I guess mount times out a bit too fast. This makes testing
>> for a successful mount a little trickier.
>>
>> I'm going to stick with growisofs for now, unless it starts giving me
>> headaches. If it does, I'll try vfat.
>>
>> Thanks.
>
> I have 2 different DVD drives, one's a Matsushita and the other is an
> LG. I have a number of DVD-RAMS that the Matsushita has trouble
> recognizing (the light blinks seemingly forever) while the LG drive
> recognizes them without any long delays. I had considered these disks
> as defective until trying them in the LG.
>
> Jerry

I insist on LG drives. I've found them to be reliable. Other drives that
I've had have all developed problems fairly quickly. Plus, LG has had
DVD-RAM support for a long time, while other drives frequently don't.

In this case, it is an LG drive that is giving me the problems. I may
have a disk gone bad because I can't currently get it formatted with any
file system I try. On the other hand, I may need to replace the drive.
I'm going to have go to the site and try the disk in a different drive.
There may be more than one bad disk, which would indicate a drive problem.

Hopefully the final word on the topic:
I've been having good luck with the following approach:
- create a bzipped tar of the /home directory
- use split to split it into 1G files to get around the UDF support bug
- try to mount the DVD-RAM as UDF. If it fails, format it then mount it
- cp the split files to the DVD-RAM, comparing after copying. If the
copy didn't work, retry it once only.

So far things seem to be working out. I'm getting an error on some
copies but so far just on one of the split files, and recopying that
file has always worked so far. Last night's backup was clean on the
first try.

I'm not thrilled with this approach because it is overly complicated.
However, it has been working reliably so far, and that is the main criteria.